Indication apparatus to indicate the output level of a pilot flame and method

ABSTRACT

The present invention concerns an indication apparatus and corresponding method to indicate the output level of a pilot flame in a gas appliance provided with a thermocouple suitable to convert the energy generated by a pilot flame, which receives gas from a pilot valve, into electric voltage to power an electro valve of the pilot valve and to keep the latter open. The apparatus comprises a first and a second connector suitable to be coupled with a positive terminal and with a negative terminal of the thermocouple, a voltage measurement circuit connected to the first and the second connector, a lighting device configured to provide a light signal, a controller device coupled with the voltage measurement circuit and with the lighting device and configured to determine the switching on of the lighting device on the basis of the output supplied by the voltage measurement circuit to provide a user with an indication of when the voltage generated by the thermocouple is greater than or equal to a predefined value sufficient to power the electro valve.

FIELD OF THE INVENTION

The present invention concerns in general an apparatus to indicate anoutput level of a pilot flame used in gas appliances provided withmanual valves and thermoelectric safety valve devices. In particular,the gas appliances in question can comprise boilers, storage waterheaters, stoves, ovens, fireplaces, or similar or comparable appliances,provided with a gas burner.

The invention also concerns the connected method to indicate the outputlevel of a pilot flame in a gas appliance.

BACKGROUND OF THE INVENTION

Gas heating appliances are known, for example boilers, or water heaters,generally provided with a main burner and a pilot burner. Normally, alsofor safety reasons, these gas appliances have sealed combustionchambers, and are provided with a pilot valve, manually drivable by auser, to supply a flow of gas to the pilot burner.

The opening of the pilot valve allows to switch on the pilot flame ofthe pilot burner by means of an ignition device, for example apiezoelectric element. The pilot flame then powers a thermocouple, whichconverts the heat into electric energy suitable to power an electrovalve that keeps the pilot valve open. The pilot burner thereforeremains switched on and burns continuously to keep the pilot flameignited to supply the ignition source for the main burner.

The gas valves and pilot burners function independently of anyconnection to the electric power inside the building in which they areinstalled.

In gas appliances of this type it is normally difficult to control thefunctioning of the pilot valve and the ignition device since the pilotflame is positioned in places that are not easily accessible to the userand is therefore difficult to see from outside the gas appliance.

When the pilot flame is first ignited, or re-ignited following amalfunctioning of the appliance, or a maintenance operation, the userhas to manually open the pilot valve, to supply gas to the pilot burner,and subsequently drive the ignition device to ignite the pilot flame,continuing to keep the valve open manually until the thermocouple isable to generate an electric voltage of sufficient value to keep thepilot valve open.

Since the pilot flame is not normally visible to the user, the usercannot understand whether the pilot flame is correctly ignited, orwhether it is supplying sufficient energy to keep the pilot valve open,so he does not know if/when he can release the manual drive.

In order to at least partly solve this problem, indication apparatusesare known, associated with the gas appliances, suitable to provide anoutput level of the pilot flame to indicate to the user when he canrelease the manual drive of the pilot valve.

For example, from U.S. Pat. No. 9,080,769 an apparatus is known toindicate an output level of a pilot flame for heating appliances,comprising a voltage measurement circuit which provides an outputindicative of a quantity of the voltage generated by the thermocouple, alighting device and a controller coupled with the thermocouple and withthe lighting device. The controller, based on the output provided by thevoltage measurement circuit, determines a switching sequence to switchon and switch off the lighting device with a defined frequency, andprovides an indication of when the voltage generated by the thermocoupleis growing toward a value sufficient to keep the pilot valve open. Inthe solution described in U.S. Pat. No. 9,080,769 the controller and thelighting device are both powered by a battery. This known solution hasthe disadvantage that the battery, having to power the two components,has a limited duration, so that it is not possible to continuouslymaintain the flashing of the lighting device.

Another known solution, described for example in U.S. Pat. No.4,770,629, describes a control system for a burner provided with a pilotflame which powers a thermoelectric generator, which supplies energy toan oscillator. The oscillator has an output that is increased to avoltage level and converted to a regulated direct current potential,which is in turn used to operate a solid state controller. Thecontroller has a sampling frequency which is visually indicated by alight-emitting diode when a suitable electric voltage is present. Thisknown solution has the disadvantage that it entails an increase in thetime required to activate the electro valve due to the fact that part ofthe energy supplied by the pilot flame is used to power the controllerand the emitter diode.

Document DE-A-199 17 488 describes an indication device for a gas burnerthat provides to use the thermocouple as a sensor to signal to a userthe actual functioning state of the burner after the initial start-upstep.

Further indicator devices are known from JP-U-S56 18984 and JP-A-S63286619.

There is therefore a need to perfect and provide an apparatus toindicate an output level of a pilot flame which overcomes at least oneof the disadvantages of the state of the art.

One purpose of the present invention is to provide an apparatus toindicate an output level of a pilot flame which does not entail anextension of the time required to power the electro valve with asufficient electric voltage and which, at the same time, can provide theuser with a reliable and immediate signal of when the manual drive canbe released.

A further purpose of the invention is to provide an apparatus toindicate the output level of the pilot flame that allows to increase thelife of a battery without the need to provide downtimes of theapparatus.

The Applicant has devised, tested and embodied the present invention toovercome the shortcomings of the state of the art and to obtain theseand other purposes and advantages.

SUMMARY OF THE INVENTION

The present invention is set forth and characterized in the independentclaims, while the dependent claims describe other characteristics of theinvention or variants to the main inventive idea.

Embodiments described here concern an indication apparatus to indicatethe output level of a pilot flame in a gas appliance, which is providedwith a thermocouple suitable to convert the energy generated by a pilotflame, which receives gas from a pilot valve, into an electric voltagesuitable to power an electro valve of the pilot valve in order to keepthe latter open. The indication apparatus comprises:

a first and a second connector suitable to be coupled with a positiveterminal and with a negative terminal of the thermocouple;

a voltage measurement circuit connected to the first and secondconnector and configured to calculate the difference in electric voltageat the heads of the terminals so as to determine the electric voltagegenerated by the thermocouple, and provide an output correlated to thedifference in voltage calculated;

a lighting device configured to provide a light signal;

a controller device, coupled with the voltage measurement circuit andwith the lighting device, and configured to determine the switching onof the lighting device on the basis of the output supplied by thevoltage measurement circuit to provide a user with an indication of whenthe voltage generated by the thermocouple is greater than or equal to apredefined value, sufficient to power the electro valve, that is, suchthat a user can stop keeping the pilot valve open manually;

a battery, connected to the controller device, and suitable to power thelatter and the voltage measurement circuit, and

a power circuit, connected between the connectors and the lightingdevice, and configured to supply the latter with the electric voltagesupplied by the thermocouple on the basis of commands received from thecontroller device, in such a way as to switch on the lighting device ina flashing manner when the voltage generated by the thermocouple isgreater than or equal to the predefined value.

When the lighting device is switched on, therefore, the user can releasethe manual drive of the pilot valve, which is kept open by the electrovalve powered by the thermocouple.

In the indication apparatus according to the invention, therefore, apart of the components is powered by a specific battery, in this casethe voltage measurement circuit and the controller device, while anotherpart of the components, in this case the lighting device, is powered bythe thermocouple.

This particular configuration allows to obtain at least the followingadvantages:

the life of the battery is increased, therefore requiring few, or no,interventions to replace it throughout the life span of the indicationapparatus;

it is possible to keep the lighting device switched on in a flashingmanner continuously without needing to provide for temporarydeactivation intervals of the indication apparatus;

the level of electric voltage sufficient to keep the electro valve openis reached more quickly, as the controller device is powered only by thebattery;

it is possible to quickly provide the user with an indication of whenthe electric voltage supplied by the thermocouple is sufficient to keepthe electro valve open autonomously.

According to some embodiments, the power circuit comprises a capacitorconnected to the lighting device and configured to accumulate a quantityof electric charge supplied by the thermocouple sufficient at least toallow the switching on of the lighting device.

According to further embodiments, the power circuit comprises a secondswitch connected in series to the lighting device, which can beselectively activated and/or deactivated by the controller device inorder to respectively allow and/or prevent the electric chargeaccumulated in the capacitor being discharged through the lightingdevice.

At the end of the charge transient of the thermocouple, as long as thepilot flame remains ignited, the lighting device can continue to flashwith a frequency correlated to the charging/discharging time of thecapacitor, to indicate the correct functioning of the gas appliance,without consuming the battery. Embodiments described here also concern agas appliance, provided with a thermocouple suitable to convert theenergy generated by a pilot flame, which receives gas from a pilotvalve, into electric voltage to power an electric valve of the pilotvalve and to keep the latter open in order to allow a pilot flame in apilot burner to be powered, and with an indication apparatus accordingto the invention connected with the thermocouple.

A purpose of the present invention is also a method to indicate theoutput level of a pilot flame in a gas appliance provided with athermocouple suitable to convert the energy generated by a pilot flame,which receives gas from a pilot valve, into electric voltage to power anelectro valve of the pilot valve and to keep the latter open, whereinthe method comprises:

detecting an electric voltage at the terminals of the thermocouple bymeans of a voltage measurement circuit;

calculating the difference in electric voltage between the twoterminals, and providing a controller device with an output signalcorrelated to the difference in electric voltage calculated in order todetermine the electric voltage generated by the thermocouple;

comparing the electric voltage generated by the thermocouple withpredefined reference values and, when the electric voltage generated bythe thermocouple is equal to or greater than a first predefined value,insufficient to power the electro valve, accumulating in a power circuita quantity of electric charge, supplied by the thermocouple, suitable toswitch on a lighting device;

keeping monitored the electric voltage generated by the thermocouple andthe quantity of electric charge accumulated in the power circuit,wherein the method provides to:

power the voltage measurement circuit and the controller device by meansof a battery;

command the power circuit, by means of the controller device, in orderto supply the lighting device with the quantity of accumulated electriccharge so that it flashes when the electric voltage generated by thethermocouple exceeds a second predefined value, sufficient to power theelectro valve, and the quantity of electric charge accumulated issufficient to switch on the lighting device.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other characteristics of the present invention will becomeapparent from the following description of some embodiments, given as anon-restrictive example, with reference to the attached drawingswherein:

FIG. 1 is a schematic view of a gas appliance provided with an apparatusto indicate the output level of the pilot flame according to embodimentsdescribed here;

FIG. 2 is a schematic diagram of an apparatus to indicate the outputlevel of the pilot flame according to embodiments described here;

FIG. 3 is a schematic diagram of an apparatus to indicate the outputlevel of the pilot flame according to variant embodiments describedhere;

FIG. 4 is a schematic diagram of an apparatus to indicate the outputlevel of the pilot flame according to further variant embodimentsdescribed here.

To facilitate comprehension, the same reference numbers have been used,where possible, to identify identical common elements in the drawings.It is understood that elements and characteristics of one embodiment canconveniently be incorporated into other embodiments without furtherclarifications.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

Embodiments described here with reference to the drawings concern anapparatus 10 to indicate the output level of a pilot flame in a gasappliance 11.

Examples of gas appliances 11 of the type in question can compriseboilers, storage water heaters, stoves, ovens, fireplaces or similar orcomparable appliances.

With reference to FIG. 1, the gas appliance 11 comprises a valve device12 configured to supply a flow of gas coming from a source of gasrespectively to a main burner 13 and to a pilot burner 14.

The valve device 12 comprises a pilot valve 15 which, in an opencondition, allows the passage of a gas flow toward the pilot burner 14.

The valve device 12 also comprises a main valve, not shown, which allowsthe passage of a flow of gas toward the main burner 13.

The pilot valve 15 is provided with a manual drive device 16 by means ofwhich a user can take it into an open condition in which the gas canflow through it, and with an electro valve 17 configured to keep it inthe open condition when it is powered with a sufficient voltage. Theelectro valve 17 can comprise, for example, a magnetic unit, or asolenoid coil which generates a magnetic field suitable to keep thepilot valve 15 open.

The gas appliance 11 also comprises an ignition device 18, for example apiezoelectric device, which can be pressed or activated by the user toignite a pilot flame in the pilot burner 14 while the pilot valve 15 iskept open by means of the manual drive device 16 driven by the user.

The valve device 12 also comprises a thermocouple 19, configured toconvert the heat provided by the pilot flame into electric voltage,which, upon reaching a sufficient value, can be applied to the electrovalve 17 to keep the pilot valve 15 open.

The apparatus 10 to indicate the output level of the pilot flame can beconnected with, or integrated, in the gas appliance 11. For example, itcan be provided that the indication apparatus 10 is made integrated in agas appliance 11 directly during the step of making the latter, or thatit is made as a separate component, connectable to newly made or alreadyexisting gas appliances 11.

According to some embodiments, the indication apparatus 10 is configuredto receive at input information on the value of the voltage generated bythe thermocouple 19 and to provide the user with an indicationcorrelated to the voltage value received, in particular to indicate tothe user when he can release the manual drive 16.

The indication apparatus 10 (FIG. 2) can comprise a first connector 20 aand a second connector 20 b configured to be connected respectively to afirst terminal T1 and a second terminal T2 of the thermocouple 19, forexample the positive terminal and the negative terminal respectively.

According to embodiments described with reference to FIG. 2, theindication apparatus 10 comprises a voltage measurement circuit 21configured to measure the electric voltage generated by the thermocouple19 and supply an output correlated to the value of the electric voltagemeasured.

The indication apparatus 10 also comprises a lighting device, forexample a LED (Light Emitting Diode) 22, and a controller device 23coupled with the voltage measurement circuit 21 and the LED 22.

The controller device 23 is configured to control the switching on ofthe LED 22 on the basis of the output supplied by the voltagemeasurement circuit 21.

According to some embodiments, the indication apparatus 10 alsocomprises a battery 24 connected to the controller device 23 andconfigured to power the controller device 23 and the voltage measurementcircuit 21 with the electric energy necessary for their functioning.

According to some embodiments, the voltage measuring circuit 21 and thecontroller device 23 can be made on the same electronic board, notshown, which is connected and powered by the battery 24.

According to some embodiments, the voltage measurement circuit 21 ispowered by the electric energy supplied by the battery 24 by means of anoutput Out3 of the controlling device 23.

The thermocouple 19, therefore, at least in an initial transitionalheating step, does not power either the voltage measurement circuit 21or the controller device 23. These therefore do not risk interrupting orinfluencing in any way the electric voltage generated by thethermocouple 19.

Furthermore, the battery 24 does not power any component of the valvedevice 12, which therefore functions independently of the state ofcharge of the battery 24.

According to one aspect of the present invention, the indicationapparatus 10 comprises a power circuit 25 coupled with the thermocouple19 and the LED 22 and configured to power the latter with the electricvoltage supplied by the thermocouple 19.

According to some embodiments, the voltage measurement circuit 21comprises an operational amplifier 26, which acts as a comparator tocalculate the difference between two values of electric voltage. Theoperational amplifier 26 is connected, by means of the first connector20 a and the second connector 20 b, to the positive T1 and negative T2terminals of the thermocouple 19, and is configured to calculate thedifference in electric voltage between the two terminals T1, T2, andsupply an output signal correlated to the difference in electric voltagecalculated.

According to possible embodiments, the non-inverting input 27 of theoperational amplifier 26, during use, is connected to the positiveterminal T1, while the inverting input 28 is connected, by means of oneor more resistances R, to the negative terminal T2, in this example casewith a common connection to earth.

According to some embodiments, the operational amplifier 26 isconnected, by means of its own output 29, to the controller device 23 tosupply the latter with the output signal correlated to the difference inelectric voltage calculated.

According to some embodiments, the controller device 23 can be amicrocontroller, a microprocessor, or other similar device suitable toreceive input signals/data, process them and provide output signals/datacorrelated to the input signals/data.

According to some embodiments, a program, or a sequence of instructions,can be stored in the controller device 23 to control the power circuit25 and determine the switching on of the LED 22 based on the inputsignals/data received.

According to some embodiments, the power circuit 25 comprises atransformer 30 provided with a primary coil 31 and a secondary coil 32,and configured to raise the voltage generated by the thermocouple 19.

According to some embodiments, the ratio between the primary coil 31 andthe secondary coil 32 is 1:n, where n can be comprised between about 50and about 150.

The primary coil 31 is connected to the terminals T1, T2 of thethermocouple 19, while the secondary coil 32 is connected to the clipsof the LED 22.

According to some embodiments, the power circuit 25 comprises acapacitor 33 configured to accumulate the electric energy supplied bythe thermocouple 19.

In particular, the capacitor 33 is configured to accumulate a quantityof electric charge at least sufficient to allow to switch on thelighting device 22.

According to some embodiments, the capacitor 33 is connected in parallelbetween the secondary coil 32 and the LED 22, and is configured toaccumulate the electric energy supplied by the thermocouple 19 andraised by the transformer 30.

According to some embodiments, the secondary coil 32, the capacitor 33and the LED 22 can have a common connection to earth.

According to some embodiments, the capacitor 33 is also connected to thecontroller device 23 by means of an input In1 of its own, so that thelatter can monitor the electric voltage at the heads of the capacitor 33and therefore the quantity of charge accumulated therein.

According to some embodiments, the power circuit 25 comprises a firstswitch 34 connected in series to the primary coil 31, which can beselectively activated/deactivated by the controller device 23 torespectively allow/prevent the passage of current through it and supplythe transformer 30 with an alternate electric current.

In particular, when the first switch 34 is active, it allows the passageof an electric current through the primary coil 31, while when it isinactive it behaves like an open circuit, preventing the passage of theelectric current.

The power circuit 25 can further comprise a second capacitor 35,connected in parallel between the thermocouple 19 and the primary coil31 and configured to accumulate electric energy when the first switch 34is inactive.

According to some embodiments, the power circuit 25 further comprises asecond switch 36 connected in series with the LED 22, which can beselectively activated/deactivated by the controller device 23 torespectively allow/prevent the electric energy accumulated in thecapacitor 33 being discharged through the LED 22.

In particular, when the second switch 36 is active it allows the passageof an electric current through the LED 22, so as to switch on thelatter, while when it is inactive it behaves like an open circuit, andprevents the passage of an electric current.

According to some embodiments, the first switch 34 and/or the secondswitch 36 can be, for example, semiconductor transistor devices, forexample of the MOSFET (Metal Oxide Semiconductor Field-EffectTransistor) type, or other similar devices.

According to further embodiments, in the power circuit 25 there is alsoa diode D connected between the secondary coil 32 and the LED 22 andconfigured to straighten the electric current at output from thesecondary coil 32 toward the capacitor 33 and the LED 22.

The functioning of the indication apparatus 10 at the moment of ignitionof the pilot flame is described below.

The controller 23 performs a detection of the electric voltage generatedby the thermocouple 19 at intervals with a defined sampling frequency.

According to some embodiments, the sampling frequency can be fixed orvary according to the conditions.

For example, the controller device 23 can be configured to detect theelectric voltage with a first frequency when the pilot flame is off orthe electric voltage Vt generated by the thermocouple 19 is lower than afirst predefined value Voff, insufficient to keep the electro valve 17open.

The first frequency can be, for example, 0.3 Hz.

The controller device 23 can be configured to detect the electricvoltage with a second frequency when the pilot flame is on, or when theelectric voltage Vt generated by the thermocouple 19 is greater than orequal to a second predefined value Von, sufficient to keep the electrovalve 17 open.

The second frequency can be lower than the first frequency, for example0.1 Hz.

When the controller device 23 detects that the electric voltage Vtgenerated by the thermocouple 19 is higher than a first threshold valueV1, it commands the first switch 34 by means of a first output Out1 toactivate/deactivate it in a controlled manner.

In this way, the transformer 30 is powered, which raises the voltagegenerated by the thermocouple 19 which is accumulated in the capacitor33 disposed downstream.

During the charge transient of the thermocouple 19, the second switch 36is in an inactive state, therefore no electric current flows through itand all the energy is accumulated in the capacitor 33.

According to some embodiments, the controller device 23 can command thefirst switch 34 by means of a PWM (Pulse Width Modulation) command witha desired duty cycle.

Furthermore, the controller device 23 keeps the electric voltage at theheads of the capacitor 33 monitored by means of the first input In1.

When the electric voltage Vt generated by the thermocouple 19 exceedsthe second predefined value Von, that is, it is sufficient to keep theelectro valve 17 open, and the quantity of electric charge stored in thecapacitor 33 is equal to or greater than a predefined threshold valueC*, sufficient to allow the switching on of the LED 22, then thecontroller 23 activates the second switch 36 by means of a second outputOut2.

In this way, the circuit branch of the LED 22 is earthed, and the chargestored in the capacitor 33 can be discharged through the LED 22, whichswitches on with a single flash.

When the LED 22 is switched on, the user can release the manual drivedevice 16 and the pilot valve 15 is kept in the open state by theelectro valve 17.

Once the capacitor 33 is discharged, the second switch 36 is deactivatedagain to allow a new accumulation of electric charge in the capacitor33.

Following the transitional step of starting and igniting the pilotflame, the LED 22 can continue to flash with a frequency correlated tothe charge/discharge speed of the capacitor 33.

By way of example, the frequency can be about 0.5 Hz, that is, one flashapproximately every 2 seconds.

In fact, as long as the electric voltage Vt generated by thethermocouple 19 remains higher than the first threshold value V1, thecontroller device 23 continues to activate/deactivate the first switch34 to charge the capacitor 33 and, when the accumulated electric chargereaches the predefined threshold value C*, it commands the activation ofthe second switch 36.

According to further embodiments, described with reference to FIG. 3,the power circuit 25 can be connected to the battery 24.

According to these solutions, the power circuit 25 can comprise aresistor 37 connected between the battery 24 and the capacitor 33.

In this case, the capacitor 33 can be pre-charged directly by thebattery 24 when it is installed, therefore the execution of the firstflash of the LED can occur as soon as the controller device verifiesthat the electric voltage Vt is equal to or greater than the secondpredefined value Von, without needing to wait for a charge transient ofthe capacitor 33 with the electric energy supplied by the thermocouple19.

According to some embodiments, the resistance value of the resistor 37can be defined in the design step so as to satisfy the followingrequirements:

it must be high enough to prevent the LED 22 from switching on by meansof the battery 24;

it must be low enough to allow the capacitor 33 to charge in a limitedperiod of time after the battery 24 has been installed.

By way of example, this period of time can be comprised between a fewseconds and a few minutes, for example less than five minutes.

According to this variant embodiment, therefore, the energy required forthe first switching on of the LED 22 at the end of the charge transientof the thermocouple 19 is supplied to the power circuit 25 by thebattery 24.

Subsequently, once normal working conditions have been reached, as longas the pilot flame remains on, the energy required to switch on the LED22 is supplied almost completely by the thermocouple 19 by means of thetransformer 30 and the capacitor 33, since the energy transfer from thebattery 24 is limited by the resistor 37.

Furthermore, when the pilot flame is switched off, the lighting devicestops flashing, and the power circuit 25 only takes from the battery 24the energy necessary for the charge transient of the capacitor 33, sincethe diode D on one side and the second switch 36 on the other preventthe passage of the electric current to the earth.

It is clear that modifications and/or additions of parts may be made tothe apparatus 10 and method to indicate the output level of a pilotflame as described heretofore, without departing from the field andscope of the present invention.

For example, according to a further embodiment described with referenceto FIG. 4, it can be provided that the controller device 23 is alsoconnected, in addition to the battery 24, to the power circuit 25.

According to these embodiments, the controller device 23 can be providedwith two distinct power branches, of which a first branch 38 isconnected to the battery 24, and a second branch 39 is connected to thepower circuit 25, and in particular to the secondary coil 32.

According to some embodiments, the two branches 38, 39 are connected ina common node 45, so that the controller device 23 is powered by thebranch 38, 39 which on each occasion has the greatest electric voltage.

According to some embodiments, a capacitor 42 can be present between thecommon node 45 and the earth, having the function of a filter andconfigured to stabilize the electric voltage supplied to the controller23.

During the initial transitional step of heating the thermocouple 19, theelectric voltage supplied by the power circuit 25 is lower than theelectric voltage supplied by the battery 24, therefore the controllerdevice 23 is powered by the latter by means of the first branch 38.

During the functioning under normal working conditions, when thethermocouple 19 has heated up, the electric voltage at the heads of thesecondary coil 32 of the power circuit 25 is generally greater than thatsupplied by the battery 24, therefore the controller device 23 ispowered by the power circuit 25 by means of the second branch 39.

This embodiment allows to further increase the duration of the battery24, since, under normal working conditions, when the pilot flame isignited, the entire apparatus 10 is powered only by the thermocouple 19.

In the event that the pilot flame goes out, and/or the electric voltageof the second branch 39 in the common node 45 falls below the electricvoltage of the battery 24, the functioning of the controlling device 23is in any case guaranteed by the battery 24.

According to some embodiments, the first branch 38 and the second branch39 comprise respective diodes 40, 41 which perform a protectivefunction. In particular, the diode 40 in the first branch 38 preventsthe electric voltage supplied by the power circuit 25 from damaging thebattery 24, while the diode 41 in the second branch 39 prevents theelectric energy supplied by the battery 24 from flowing in the form ofelectric current toward the power circuit 25 and toward the LED.

According to some embodiments, the apparatus 10 comprises a voltagelimiting circuit 46 connected between the controller device 23 and thecommon node 45 and configured to limit the voltage at input to thecontroller device 23 so as to prevent possible damage to the latter.

According to possible embodiments, the voltage limiting circuit 46 cancomprise a resistor 43 and a third switch 44, which can be selectivelyactivated by the controller device 23, disposed in series one after theother.

According to some embodiments, the third switch 44 can be activated bythe controller device 23 by means of an output Out4 of its own, when itdetects that the electric voltage at the input Vcc exceeds apredetermined voltage value, so as to allow the passage of an electriccurrent through the resistor 43 to the earth, thus reducing the electricvoltage at input to the controller device 23.

It is also clear that, although the present invention has been describedwith reference to some specific examples, a person of skill in the artshall certainly be able to achieve many other equivalent forms ofapparatus 10 and method to indicate the output level of a pilot flame,having the characteristics as set forth in the claims and hence allcoming within the field of protection defined thereby.

1. An indication apparatus to indicate the output level of a pilot flame in a gas appliance provided with a thermocouple suitable to convert the energy generated by a pilot flame, which receives gas from a pilot valve, into electric voltage to power an electro valve of the pilot valve and to keep the latter open, characterized in that said apparatus comprises: a first and a second connector suitable to be coupled with a positive terminal and with a negative terminal of the thermocouple; a voltage measurement circuit connected to said first and second connectors and configured to calculate the difference in electric voltage at the heads of the terminals to determine the electric voltage generated by the thermocouple and to provide an output correlated to the difference in voltage calculated; a lighting device configured to provide a light signal; a controller device coupled with the voltage measurement circuit and with the lighting device and configured to determine the switching on of said lighting device on the basis of the output supplied by the voltage measurement circuit to provide a user with an indication of when the voltage generated by the thermocouple is greater than or equal to a predefined value sufficient to power the electro valve; a battery connected to said controller device, and configured to power the latter and the voltage measurement circuit, and a power circuit connected between said connectors and said lighting device, and comprising a capacitor configured to accumulate a quantity of electric charge supplied by the thermocouple at least sufficient to allow the switching on of said lighting device, said power circuit being configured to power the latter with the electric voltage supplied by said capacitor on the basis of commands received from said controller device in such a way as to switch on said lighting device in a flashing manner when the voltage generated by the thermocouple is greater than or equal to said predefined value.
 2. The indication apparatus of claim 1, wherein said power circuit comprises a second switch connected in series to said lighting device, which can be selectively activated/deactivated by said controller device in order to respectively allow/prevent the electric charge accumulated in said capacitor being discharged through said lighting device.
 3. The indication apparatus of claim 2, wherein said indication apparatus comprises a transformer configured to raise the electric voltage generated by the thermocouple and provided with a primary coil connected to the first and to the second connector, and with a secondary coil connected to the heads of said lighting device, wherein said capacitor is connected in parallel between said secondary coil and said lighting device, and is configured to accumulate the electric voltage supplied by said transformer.
 4. The indication apparatus of claim 3, wherein said power circuit comprises a first switch connected in series to said primary coil, which can be selectively activated/deactivated by said controller device in order to respectively allow/prevent the passage of current through it to provide the transformer with an alternating electric current.
 5. The indication apparatus as in any of claim 1, wherein said capacitor is connected to said battery by means of a resistor having a resistance value such as to prevent the switching on of said lighting device only by means of said battery.
 6. The indication apparatus of claim 1, wherein said voltage measurement circuit comprises an operational amplifier connectable by means of the first connector and the second connector to the positive and negative terminals of the thermocouple, and is configured to calculate the difference in electric voltage between the two terminals, and to supply said controller device with an output signal correlated to the difference in electric voltage calculated.
 7. The indication apparatus of claim 1, wherein said controller device is connected by means of a first circuit branch to said battery and by means of a second circuit branch to said power circuit, wherein said first branch and said second branch are connected in a common node.
 8. A gas appliance comprising a valve device configured to supply a flow of gas to a main burner and to a pilot burner, and provided with a pilot valve which can be driven manually with a manual drive device by means of which a user can take it to an open condition to allow the passage of the gas through it, and a electro valve configured to keep it in the open condition when it is powered with sufficient voltage, and with a thermocouple configured to convert the heat supplied by a pilot flame of the pilot burner into an electric voltage suitable to power the electro valve to keep the pilot valve open, characterized in that said gas appliance comprises the indication apparatus of claim 1 connected to the terminals of said thermocouple.
 9. A method to indicate the output level of a pilot flame in a gas appliance provided with a thermocouple suitable to convert the energy generated by a pilot flame, which receives gas from a pilot valve, into an electric voltage suitable to power an electro valve of the pilot valve and to keep the latter open, characterized in that said method comprises: detecting an electric voltage at the terminals of the thermocouple by means of a voltage measurement circuit; calculating the difference in electric voltage between the two terminals, and providing a controller device with an output signal correlated to the difference in electric voltage calculated in order to determine the electric voltage generated by the thermocouple; comparing the electric voltage generated by the thermocouple with predefined reference values and, when said electric voltage is equal to or greater than a first predefined value, insufficient to power the electro valve, accumulating in a capacitor of a power circuit connected between said thermocouple and said lighting device a quantity of electric charge, supplied by said thermocouple, and suitable to switch on a lighting device; keeping monitored said electric voltage generated by the thermocouple and said quantity of electric charge accumulated in the power circuit, wherein the method provides to: power said voltage measurement circuit and said controller device by means of a battery; command, by means of said controller device, said power circuit in order to supply said lighting device with said quantity of accumulated electric charge so that it flashes, when the electric voltage generated by the thermocouple is greater than or equal to a second predefined value, sufficient to power the electro valve, and the quantity of electric charge accumulated is sufficient to switch on said lighting device.
 10. The method of claim 9, said method provides to accumulate said electric charge in said capacitor by means of a transformer connected between the thermocouple and the capacitor, wherein the method provides to selectively activate and/or deactivate a first switch connected in series to a primary coil of said transformer by means of said controller device in order to respectively allow and/or prevent the passage of current through it to provide the transformer with an alternating electric current when the voltage generated by the thermocouple is greater than or equal to the first predefined value.
 11. The method in of claim 10, wherein, in order to switch on the lighting device (22) with said quantity of accumulated electric charge, the method provides to activate a second switch, connected in series to said lighting device, by means of said controller device, to allow the electric charge accumulated in said capacitor to discharge through said lighting device and switch on the latter.
 12. The method claim 10, wherein said method provides to pre-charge said capacitor with a quantity of charge provided by said battery at the moment said battery is installed.
 13. The method of claim 9, further comprising powering said controller device by means of the power circuit with the energy supplied by said thermocouple, when, under normal working conditions, the electric voltage of said power circuit is greater than the electric voltage of said battery. 